Comments: Just picked this shoe up the day before my Half last weekend. Did a run to make sure there wouldn't be any rubbing issues and they actually performed very well on my feet for the Half. I've used the 155's for 2-years, well over 1,000 miles on them with a few holes in the forefoot, so I was looking for a shoe as similar as possible but with better durability. The 138 is going to be significantly more durable and provides a decent amount of comfort for distance, while maintaining enough feedback for proprioception. Similar to Inov-8's other 3mm-down shoes, the 138 doesn't effect your natural gait and promotes a very efficient stride. Without the sock-liner, you can feel the seams of the shoe so I'm not sure how comfortable running without it will be. Forefoot is not as roomy as the 155 (in my opinion) but certainly enough room for most feet. Also, I wore a size-8.5 for the 155 and I am using the size-9 for the 138. In my opinion, whatever the road-distance, if you're into maintaining efficient running form, this shoe is a great addition to your collection. Plan to use it for my Full in October. God's Peace!From: Christopher, Milwaukee, WI

Comments: This shoe is a great racing flat. If you were wondering, it is zero drop with the insoles removed and it is a 3mm drop when you have the insoles in. Most of the shoes I wear are zero drop but with this shoe I preferred having the 3mm insoles in, the difference was not that significant, especially for speed work. It is also more comfortable sockless with the insoles in than without them. Another thing that isn't mentioned in the description is that it has a single burrito style tongue similar to the New Balance Road Zero MR00. This is a much firmer ride to the NB MR00 however. It is a similar fit to the Invo-8 Bare-X Lite 150 and the Inov-8 Road X-Lite 155 which I wear a size 11 in both of those and a size 11 in the Road-X-Treme 138. The durability of this shoe will be better than the 150 and 155 when comparing the materials of the outsoles. The 138 has better traction in dry conditions so far. I haven't tested them in the wet yet. Overall a very good minimal shoe, light weight, comfortable, and my go-to shoe for speed work and races up to 10k (I prefer more cushion for longer races and runs; check out the Altra The One if you have the same preference).From: Josh, Dallas, Texas, USA